The present invention relates to a jack apparatus for heavy duty lifting, and more particularly relates to a jack incorporating a pair of screw jacks supporting a yoke in a manner providing high load lifting capabilities, low (and adjustable) initial starting point for lifting, safe lifting without need for separate jack stand or locking mechanism, close-to-obstruction lifting (e.g. where an obstruction is close to a desired lift point), adaptability to different energy-based drive units (such as hydraulic, electric and/or pneumatic), and modularity (for easy assembly or repair or maintenance of the jack apparatus). Also, the present invention relates to a jack system and method using a control to simultaneously operate several of the jack apparatus for simultaneous lifting at multiple points on equipment. The present system is particularly useful in heavy industry such as mining and construction, but is not believed to be limited to only those industries.
Jack systems for lifting heavy objects are often needed for heavy machinery and equipment, such as are used in mining, construction, farming, earth-moving, and industrial applications. Many times, the equipment must be lifted on site, including outdoors. Safety is a significant concern since the equipment can be massive, yet it is difficult to police safe use due to the locations where the jacks are used. Known jack systems suffer from several limitations, including the need for use of separate jack stands to ensure the equipment does not unexpectedly lower and injure a worker. Also, known jacks are limited in their ability to jack at different starting heights (e.g. very low ground clearance conditions) and to different ending heights (e.g. a combination of high initial ground clearance and high lift requirement to satisfy the maintenance need.) Additional characteristics are desired that are often not found in existing jack systems, such as modularity (so that components can be replaced easily in the field), ability to use different power sources to operate the jacks (e.g. electric, or hydraulic, or pneumatic power), portability (i.e. durable enough for heavy-duty use but sufficiently light and portable for movement over rough terrain), safety against unexpected lowering of the jack even when a jack stand is not used (i.e. so that there is less risk of a worker bypassing safety procedures), close-to obstruction lifting where the obstruction is only inches for a desired lift point (such as when a wheel is close to a frame lift point). Also, a jack system is desired that can be used in a system where several jacks are controlled simultaneously for simultaneous lifting of equipment at multiple points on the equipment.